As the use of mercury lamps is regulated, UV-LEDs capable of emitting short wavelength light, especially UV band light is regarded promising as the replacement. While LEDs can produce light of arbitrary wavelength, LEDs of wavelength for a particular application are developed. For example, wavelength 265 nm in the UV region is known effective for sterilization. UV-LEDs adapted to emit light of wavelength 265 nm are developed for the sterilization application. Even when optical devices of 265 nm are in constant supply, it is difficult to use the optical devices without packages. It is thus required to package the UV-LED while maximizing the light extraction efficiency from the UV-LED.
When optical devices capable of emitting light of long wavelength such as IR region including LEDs are packaged, an adhesive is necessary for bonding a window member to a receptacle having the optical device mounted in place. There are known a variety of adhesives including organic adhesives such as epoxy resin and acrylic resin base adhesives and glass frits.
For example, Patent Document 1 proposes sealing of inorganic substrates of strengthened glass having a melting point of about 300° C. using a paste obtained by mixing a glass frit with a microwave coupling agent as an adhesive, for purposes such as solar cell encapsulation and OLED packaging. This method is successful in bonding substrates by applying microwave to the adhesive area, without losing the strength of strengthened glass used as window member.
Patent Document 2 discloses to use a UV-curable acrylic liquid resin or thermosetting resin as the adhesive in bonding micro lenses.
Patent Document 3 describes packaging of electronic devices using a vanadium-based low-melting glass having a coefficient of linear thermal expansion close to the coefficients of linear thermal expansion of base substrate and lid as the adhesive. This method achieves fully hermetic packaging.